574 CHARLES KEYES 



laid deposits of this age in the region; but Miocene and PKocene 

 deposits seem to be chiefly, if not entirely, continental in character. 



It is quite probable, therefore, that the tops of the monadnocks 

 which rise above the level of the highland plain of Lake Superior 

 represent approximately the level of the Comanchean peneplain; 

 and that the present plain of that region is Eocene in date. This 

 interpretation has many points supporting it; and but few or none 

 against it. Around Lake Superior glacial action has entirely 

 removed the evidence for the ready determination of these sup- 

 porting facts. The strongest and most convincing testimony comes 

 from neighboring localities ; and the several lines of evidence appear 

 to be wholly congruous and mutually supporting. 



For the formation of the Lake Superior highlands an Eocene 

 age appears to be conclusive. The necessary consequences are 

 far-reaching. It calls for an examination anew of the geographic 

 development of a large part of the northeastern section of the 

 North American continent. 



